<h4>Tool</h4><table border="0"><tr><td valign="top"><b>Name</b></td><td valign="top">Stream Power Index</td></tr><tr><td valign="top"><b>ID</b></td><td valign="top">21</td></tr><tr><td valign="top"><b>Author</b></td><td valign="top">O.Conrad (c) 2003</td></tr><tr><td valign="top"><b>Specification</b></td><td valign="top">grid</td></tr></table><hr><h4>Description</h4>Calculation of stream power index based on slope and specific catchment area (SCA).
SPI = SCA * tan(Slope)

References:

Moore, I.D., Grayson, R.B., Ladson, A.R. (1991):
'Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications'
Hydrological Processes, Vol.5, No.1
<hr><h4>Parameters</h4><table border="1" width="100%" valign="top" cellpadding="5" rules="all"><tr><th>Name</th><th>Type</th><th>Identifier</th><th>Description</th><th>Constraints</th></tr>
<tr><th colspan="5">Input</th></tr><tr><td>Slope </td><td>Grid (input)</td><td>SLOPE</td><td></td><td></td></tr><tr><td>Catchment Area </td><td>Grid (input)</td><td>AREA</td><td></td><td></td></tr><tr><th colspan="5">Output</th></tr><tr><td>Stream Power Index</td><td>Grid (output)</td><td>SPI</td><td></td><td></td></tr><tr><th colspan="5">Options</th></tr><tr><td>Area Conversion</td><td>Choice</td><td>CONV</td><td></td><td>Available Choices:
[0] no conversion (areas already given as specific catchment area)
[1] 1 / cell size (pseudo specific catchment area)
Default: 0</td></tr></table>